Lubricants and lubricant concentrates perform a variety of functions in automotive applications. One of the most important functions is to reduce friction and wear in moving machinery. Also, lubricants protect metal surfaces against rust and corrosion, act as heat transfer agents, flush out contaminants, absorb shocks, and form seals.
The performance of lubricant oils is a function of the additive composition they contain. The most common types of additives are: antiwear agents, antifoams, emulsifiers, extreme pressure (EP) agents, antioxidants, ashless dispersants, viscosity-index improvers, rust inhibitors, corrosion inhibitors, friction modifiers, and pour point depressants.
Lubricant additives deposit lubricating films on the surface of moving parts which reduces friction. One of the indictions of the friction reducing properties of a lubricating oil is the coefficient of friction. The lower the coefficient of friction, the less the wear. The viscosity-temperature index i.e., the index that characterizes the relationship between oil viscosity and temperature, and the pressure-viscosity index are also important in friction reduction. In addition, factors such as material combinations and their mixability in each other, their solubility in base oils, atomic size of metals in lubricants, valency, molecular structure of materials, electrochemical activity and the type of intermolecular forces between molecules are also important in reducing the coefficient of friction.
Among factors which contribute to the effectiveness of a lubricant oil are high temperature, high loads, and EP or film strength. EP refers to the action of the lubricant against metal-to-metal contact. With an effective EP or film strength, metal scoring and welding can be prevented. Generally, EP property is needed where high torque and rubbing speeds exist.
Certain lubricating oil compositions are known in the art. For instance, U.S. Pat. No. 4,612,129, incorporated herein in its entirety by reference, discloses lubricating oil compositions containing at least one metal salt of at least one dithiocarbamic acid of the formula R.sub.1 (R.sub.2)N-CSSH.
U.S. Pat. No. 4,917,809, incorporated herein in its entirety by reference, discloses a lubricating composition containing benzotriazoles and olefin copolymers.
U.S. Pat. No. 3,876,550, incorporated herein in its entirety by reference, discloses lubricant compositions containing borated hydrocarbon-substituted succinic acid compounds and hindered phenolics.
A problem with prior lubricant compositions is that they often contained hazardous materials such as zinc dialkyldithiophosphate (ZDTP), phosphorous and halogens. In view of the increasing strictness of environmental regulations, as well as the increased awareness of environmental issues, there has developed a need to produce lubricating oils and concentrated additives for lubricating oils that are in compliance with human and environmental safety standards, while at the same time, facilitate optimum engine performance and protection.
The present invention meets this need by providing improved lubricating oils and concentrated additives for lubricating oils having competitive manufacturing cost efficiency and that already meet or exceed new European environmental standards established for implementation in 1997. The oils and concentrated additives of the present invention contain ingredients that have never before been used in engine lubricants.